Post-fire impacts in the Central European Uplands: linking surface dynamics and contamination hazards in unmanaged forests to landscape and forest recovery

Central Europe is emerging as a new fire region, with climate change increasing the likelihood of forest fires. In contrast to “classical” fire regions, such as the Mediterranean, little is known about Earth surface dynamics following fires in Central European upland forests. In August 2022, a 13-hectare fire burned a spruce forest disturbed by a wide-spread bark beetle infestation in Harz National Park. We monitored the site at roughly six-month intervals, comparing burned and unburned areas using unoccupied aerial vehicles equipped with multispectral, thermal, high-resolution RGB, and LiDAR sensors. Derived orthoimages, 3D point clouds, and canopy height were employed to estimate standing deadwood, succession indicators such as fractional vegetation cover, microclimate regimes, and small-scale morphological changes. We additionally collected soil samples with different burn severities, including soils associated with charcoal kilns that repesent legacies of past land use, to better understand post-fire nutrient and pollutant dynamics over time. We particularly focused on the point-source contamination by polycyclic aromatic hydrocarbons, which are considered toxic to organisms, including human health, and that could be measured in soils sampled over time. We found a dynamic setting associated with fire severity, subsurface tunneling, and the long-term legacy of granite landscape evolution, collectively affecting post-fire mass movements, vegetation recovery, and pollutant loads. Here, we present first insights into deadwood breakdown, vegetation succession, surface erosion and soil property changes, to bridge the knowledge gap between well-studied fire-prone regions and emerging ones like Central Europe and to provide base-knowledge for future research and management strategies.